Sexyness, man is usually confidence, and how you dress yourself.
Some people suit dressing all messy , some suit all neat. Whatever suits your character is sexy. Do you hair, dosent matter what style, as long as its not ordinary, and not too freaky, it will be sexy "must suit you ofcourse". Feeling confident of your hair, your looks, your clothes, how you walk, how you portray , and your overall image, evewn your voice determines your sexyness, you can see who is and isnt. You can even be sexy in a potato bag if u wanted. Its the projection of your image, and how you get percieved. If you are a nerd, and u wear a girls dress to a dress up party , you look like a damn weird fool. If you are a guy with confidence charm, and sexyness you can wear a dress and be cool? A little odd example but u get my drift?